Radio Frequency identification (RFID) tags are increasingly being used to track multiple objects throughout a specified system. For example, RFID tags are being used on warehouse pallets to track the location of goods in a warehouse or verify the authenticity of tickets at a venue.
An RFID tag is often implemented as a tiny integrated chip (IC) (hereinafter “mu-chip”) attached to an antenna. The IC stores a small amount of data, such as an. ID number, and the antenna is used to communicate with a reader. For example, one particular existing Hitachi mu-chip stores 128 bits of read-only data and communicates using a frequency of 2.45 GHz. Tags can be either active, which means they contain a battery, or passive. In the case of passive tags an external source, e.g., the tag reader, provides the power needed for communication. In many applications, direct line of sight is not necessary to read a tag; tag reading can be accomplished provided the RF signal is strong enough to go between the tag and reader. With some readers and tags it is also possible to read multiple tags simultaneously. RFID tags are designed to work at specific radio frequencies depending upon the physical characteristics of the antenna. Higher frequencies enable faster communication and typically larger read ranges. Lower frequencies often work better in the vicinity of metals or liquids. In general, the most suitable tag design depends on the specific application.
RFID tags can be very small which enables a number of different applications. For example, a Hitachi mu-chip can be applied to paper currency to combat counterfeit bills. This is possible because of the small size of the mu-chip; some embodiments of a mu-chip transponder measure 0.4 mm square and 0.15 mm thick.
One example of an existing RFID tag is a Hitachi mu-chip coupled to an antenna. Hitachi's mu-chip aids upwards communication from real-world objects to virtual ones. The RFID mu-chip 100, as shown in functional circuit blocks in FIG. 1, is 0.06-mm thick and 0.4-mm long on each side. The RFID mu-chip 100 includes an analog circuit 102 and a digital circuit 104. The analog circuit 102 includes a power rectifier module 106, a power-on reset module 108, and a clock extraction module 110. The digital circuit 104 includes a 10-bit counter 112, a decoder 114, and a 128-bit ROM 116. The analog circuit 102 is coupled to the digital circuit 104. The analog circuit 102 is also coupled to antenna terminals 118 and 120. By applying suitable packaging techniques, manufacturers can embed mu-chips in micro-objects. The 2.45 GHz band frequency, used for radio communication signaling between the mu-chip and a sensor, similar to that used by Bluetooth technology, enables use of a small sensor device.
The current mu-chip function is to return the 128-bit identification data stored in 128 bit ROM 116 upon receiving the radio wave from an external sensor. This data is the same length as IPv6 addresses. The mu-chip's characteristics give it an advantage in certain applications over other approaches to identifying and tracking products.
The mu-chip is similar to the bar code in that both give identification numbers to objects. One major difference is that mu-chips can be attached to smaller objects than a bar code can be attached to, because a bar code has a larger surface area than a mu-chip. Therefore, the mu-chip enables handling of objects efficiently in a wider range of applications than the bar code. Furthermore, copying mu-chips is much more difficult than copying bar codes. Thus, mu-chips can handle objects more securely than bar codes, preventing the forgery of security papers and providing counterfeit protection for branded products.
Current mu-chips retain 128-bit ID information in ROM 116, which is written only once at manufacturing time. The 128-bit ID information in ROM 116 cannot be modified after shipment.
FIG. 2 shows an example of the basic structure of mu-chip operations in a block diagram 200. Diagram 200 illustrates mu-chip 202 embedded in product 204. Mu-chip 202 may be mu-chip 100 of FIG. 1. The mu-chip 202 includes an amplifier 206 and a ROM 208 including system/application data and an ID code. An antenna 210 is also embedded in the product 204, and the antenna 210 is coupled to the mu-chip 202.
One counter-measure is to embed a mu-chip into security papers or brand name products and verify authenticity with a sensor reading. In this case, a tag reader including a transmitter and a read sensor 212, transmits signals to the mu-chip 202, e.g., using a 2.45 GHz microwave carrier, which is used to power on and activate the mu-chip 202. This results in the mu-chip 202 transmitting its stored 128-bit ID information via antenna 210. The sensor 212 receives and reads the return data, recovering the 128-bit ID information which has been sent via microwaves 214. With the antenna 210, the mu-chip is readable by the sensor 212 within a 30-cm range, instead of proximate range for reading a mu-chip 202 that is applicable when antenna 210 is not used. The output from the sensor 212 is sent to terminal 216. The output from terminal 216 is then sent to a server 218 which processes the data. The server 218 is part of a control center 220. In both cases, the security audit mechanism implemented in a server 218 checks for any abnormality by analyzing network-transmitted records. The system signals an alarm when it detects an alleged counterfeit chip, identification numbers transmitted at the same time from different locations, or any other predefined abnormality.
One design uses a built-in 100-pf capacitor formed by the gate oxide of the MOS transistor as a power supply, eliminating the need for batteries. The minimum operating voltage of the chip's digital chips is 0.5V. This chip has attached to it a thin-film external antenna. The chip terminals (118, 120) are connected to the antenna by an anisotropic conductive film (ACF). This type of structure results in a 0.15 mm thin transponder. The maximum communication distance between the mu-chip and a reader is expected to be 300 mm at a reader power of 300 m W. The RFID tag includes the mu-chip circuit and antenna.
The mu-chip 100 is one example of a RFID circuit, and other types of chip circuits and antennas are also available.
One potential application for RFID tags is for use with discs including Digital Versatile Discs (DVDs) and/or Compact Discs (CDs). Previously, attaching RFID tags to Digital Versatile Discs (DVDs) and Compact Discs (CDs) has been attempted. The term disc is intended to be used here interchangeably with the term disk which is also used sometimes. The physical characteristics of DVDs and CDs have precluded previous attempts to find a solution which works with a wide variety of such discs in a cost effective manner. The area of the disc which could be used to contain a RFID tag is limited because most of the disc surface needs to be accessible to the disc reader mechanism in order for the disc to function. In fact, the only consistently available space on almost all disc designs on which to put an RFID tag is the hub area, e.g., the 40 mm diameter hub present in many disc designs. Since the hub area is reserved for the clamping mechanism, it is universally available regardless of the specific disc type and whether the data surface is only on one side or is on two sides.
The data area of DVD's and CD's comprises a thin sputtered metallization film to permit reading by the laser mechanism. Historically, this metallization covered the entire data area, but did not extend beyond it. Specifically, the hub area at the center of the disc, that contains no data, had typically not been metallized. The metallization formed an annulus from the outside of the hub to the outside of the disc, even though the printing on single-sided discs may have extended across the entire surface. These types of discs, with no metallization in the hub area, provide less obstacles to RFID tagging than discs with metallization on the hub.
Recently DVD manufacturers have begun creating discs where the metallization extends into the hub area, almost to the center hole. Essentially the metallization is an annulus with a smaller inner diameter and the same outer diameter as regular DVD's. One reason for the increased metallization is for aesthetic purposes. These classes of discs can be described as metallized hub discs, and an increasing number of movie studio titles are delivered on these discs. Some CDs may also use a metallized hub.
FIG. 3 shows an example of a metallized hub disc 300. Disc 300 may be a DVD or CD Disc. Disc 300 includes a metallized sputtering data area 302 forming an outer ring, a metallized sputtering hub area 304 forming an intermediate ring, and a clear inner rim 306 forming an inner ring. FIG. 4 shows an example of a disc 400 with a non-metallized hub. Disc 400 may be a DVD or CD Disc. Disc 400 includes a metallized sputtering data area 402 forming an outer ring, a hub area 404 with no metallized sputtering forming an intermediate ring, and a clear inner rim 406 forming an inner ring.
A technical problem with metallized hub discs for RFID tagging is that the metallization extends into the hub area where if the RFID label is attached, the metallization effectively prevents the tag from operating. Tags that might work well, from a communications standpoint, on non-metallized hub discs do not function on the metallized hub disc variety, making universal application very difficult.
It would be advantageous if RFID tags could be developed that can inexpensively and/or reliably overcome the functional inoperability associated with radio frequency identification (RFID) tags when attached to discs that have metallization sputtering in the disc hub area, e.g., to within 4 mm of the center hole of the disc. It would also be beneficial to have RFID tags that could be universally used on a wide range of disc types, e.g., CDs, DVDs, one sided, two sided, with and without metallized hub area and future formats.
RFID tag use and problems pertinent to disc applications will be further discussed. DVD and CD item level disc inventory applications abound. Public and private libraries and disc rental enterprises could benefit from RFID tags. A potential benefit over other inventory and tracking methods such as bar codes is that RFID tags facilitate non-line of site tag reading capability, e.g., speeding processing of a disc. In addition by tagging individual discs with RFID tags, rather than tagging disc carriers such as jewel cases, as is typically the practice with bar codes applied to disc carriers, the reliability of the tracking is improved. These benefits of RFID disc tagging can also provide cost reductions, e.g., as manual labor operations are reduced and time associated with correcting errors such as a mismatched bar coded sleeve with a disc is reduced. Most current applications of RFID to optical discs involve tagging the disc carrier. Discrepancies can be expected when the carrier and the disc title inside the carrier are inconsistent, either by accident or fraud. Tagging the disc itself is the one solution to passively and positively identify a disc.
Thus, it should be appreciated that there is a need to be able to universally and reliably tag and read most or all DVDs and CDs that have both metallized and non-metallized hub areas at a price point that is generally valuable to the end user community from both the tag and the tag tracking application deployment perspectives. Typically, large scale inventories of discs will include discs of both hub types. It is also possible that clear and metallized hub discs may be used interchangeably on an identical disc title during different manufacturing batches. A key market driver to the adoption of an RFID tag to discs is likely to be that the RFID tag be capable of universal application to most or all possible existing and future discs and the universal RFID tag function acceptably on most or all possible existing discs.
A universal tag design would afford production scale efficiencies that tend to bring large volume tag unit manufacturing costs down. The universal tag design facilitates ease of deployment of the tags on discs because one design fits most or all disc types. In such a design implementation of a RFID tag, no special segregation of discs or special processing by type of disc would required during the application of tags to the discs since such an RFID tag would be functionally operational with discs containing either metallized or non-metallized hubs.
Some prior technology issues and problems will now be discussed. CDs and DVDs are typically made of polycarbonate plastic with a layer of aluminum sputtering. This metallic layer electromagnetically couples to the RFID antenna and affects radio frequency transmissions, often reducing and sometimes completely impairing tag interrogation effectiveness and read reliability. Prior technologies at lower radio frequencies are not effective at overcoming read reliability difficulties associated with discs possessing a metallized hub.
13.56 MHz RFID tags are less susceptible to the interference interaction of the metal in the disc than are lower radio frequency RFID tags, but these tags are not immune to this interference problem. One known example is a specialized booster antenna label that works in conjunction with a circular coil 13.56 MHz RFID tag placed in the disc's clear hub. The booster label amplifies the RF signal of the hub tag by means of an auxiliary RF antenna that is placed over the disc's outer edge. The clear plastic overlay therefore covers the entire surface of the disc adding weight and cost. The booster disc labeling system may not work with metallized hub tags and is priced at a high level relative to the disc price. This price point is only effective in tracking the most valuable of disc inventories, and this technology is not usable with double-sided discs.
915 MHz RFID tags can be designed to effectively function on clear hub discs. However, this tag's functioning would be impaired on metallized hub discs. The hub metallization will interfere with the tag's performance by adversely interacting with the RFID antenna. If 915 MHz tags are used with metallized hub discs, additional design solutions will likely be needed adding cost, weight and/or thickness to the resulting tag design. Therefore, designing a single 915 MHz tag that is readable with both a metallized hub and clear hub disc is expected to be extremely difficult, if not impossible.
Various prior technologies utilizing tags designed for the 2.45 GHz frequency are rather costly. In addition, many 2.45 GHz tags are produced on heavy chip board stock and are too thick and heavy to apply to discs.
The existing solutions use rather large and thick-sized integrated chip (IC) chips which negatively affect the production cost of the RFID tag. The thicker IC chip may fail or disconnect from its antenna if positioned under or close to a disc drive internal clamping mechanism. Discs need to spin at very high speeds. Additional unbalanced weight on a disc can negatively affect the viability of a tag's use on a disc. Unbalanced weight will induce wobble on the spinning disc. Accordingly, any appreciable additional weight could affect the functioning of a disc drive. Standards for disc characteristics are very specific. Motors and other parts inside disc drives are built around these standards. The addition of an RFID tag on a disc changes the physical characteristics of the disc which may negatively affect some makes of drives, particularly if the tag is heavy. Lastly, overall tag thickness can adversely affect performance of the disc drive clamping mechanisms if the thick tag is placed in the disc hub area. Insecurely clamping a disc could result in an inability to read the disc or damage to the clamping mechanism, the disc, the RFID tag or the optical drive.
In view of the above, there is a need for new RFID tag designs which could be used to tag discs. It would be advantageous if such a new RFID disc tag was universally applicable to both CDs and DVDs, one and two sided, with and without metallized hub. It would also be beneficial if such a new RFID disc tag could be read from either side of the disc. Since physical characteristics of an RFID tag to be applied to a disc are a significant consideration, it would be useful if a new RFID disc tag incorporated features directed at addressing at least some these design goals: minimalization of tag weight, minimalization of tag thickness, minimalization of tag size, control of weight imbalance, damage resistance to hub clamping pressure.
Since cost is also a significant consideration in a deployment system, it would be beneficial if a new RFID disc tag could be usable with existing tag reader system equipment currently available. To benefit from the cost advantages of large scale production, it would be beneficial if a new RFID disc tag, or at least a portion of the tag, was similar to a currently produced widely used RFID tag.